The flat panel display devices possess many merits of thin frame, power saving, no radiation, etc. and have been widely used. The present flat panel display devices at present mainly comprise the Liquid Crystal Display (LCD) and the Organic Light Emitting Display (OLED).
The thin film transistor (TFT) is an important component of the flat panel display device. The TFTs can be formed on a glass substrate and a plastic substrate and generally employed as switch elements and driving elements utilized such as flat panel displays, LCDs, OLEDs and et cetera.
The oxide semiconductor TFT technology is the most popular skill at present. Because the oxide semiconductor has higher electron mobility and in comparison with the Low Temperature Poly-silicon (LTPS), the oxide semiconductor manufacture process is simpler and possesses higher compatibility with the amorphous silicon process, it can be applicable to the skill fields of LCD, OLED flat panel display devices and etc. Because it fits the new generation production lines and has possible applications for displays with Large, Middle and Small sizes. The oxide semiconductor has the great opportunity of application development.
At present, in the active array flat panel display device, the TFT substrate generally utilizes the single-gate oxide semiconductor thin film transistor (Single-Gate TFT). The dual gate oxide semiconductor thin film transistor (Dual-Gate) possesses better performance than the single gate oxide semiconductor thin film transistor, For example, the electron mobility is higher, and the current of activation state is larger, and the subthreshold swing is smaller, and the stability and the uniformity of the threshold voltage are better, and the gate voltage bias and the light stability are better.
In the OLED display device, the importance of the threshold voltage is significant. The stable, uniform threshold voltage can make the display brightness of the OLED be more even and the display quality be higher. As shown in FIG. 1, a structure of a dual gate oxide semiconductor TFT substrate applicable for the OLED according to prior art comprises a substrate 100, a first bottom gate 210 and a second bottom gate 220 on the substrate 100, a gate isolation layer 300 on the substrate 100 and the first bottom gate 210 and the second bottom gate 220, a first oxide semiconductor layer 410 and a second oxide semiconductor layer 420 on the gate isolation layer 300 respectively above the first bottom gate 210 and the second bottom gate 220, an etching stopper layer 500 on the first oxide semiconductor layer 410, the second oxide semiconductor layer 420 and the gate isolation layer 300, a first source/a first drain 610 and a second source/a second drain 620 on the etching stopper layer 500, a passivation layer 700 on the first source/the first drain 610, the second source/the second drain 620 and the etching stopper layer 500, a first top gate 810 on the passivation layer 700 above the first source/the first drain 610, a second top gate 820 on the passivation layer 700 above the second source/the second drain 620, an interlayer insulation layer 900 on the first top gate 810, the second top gate 820 and the passivation layer 700, a first flat layer 910 on the interlayer insulation layer 900, an ITO anode 1100 on the first flat layer 910 and a second flat layer 920 on the ITO anode 1100 and the first flat layer 910.
The etching stopper layer 500 is formed with two first via holes 510 correspondingly above the first oxide semiconductor layer 410, and is formed with two second via holes 520 correspondingly above the second oxide semiconductor layer 420, and the first source/the first drain 610 and the second source/the second drain 620 respectively contact with the first oxide semiconductor layer 410 and the second oxide semiconductor layer 420 through the first via holes 510 and the second via holes 520; the passivation layer 700, the interlayer insulation layer 900 and the first flat layer 910 are formed with a third via hole 530 correspondingly above the first source/the first drain 610, and the ITO anode 1100 contacts with the first source/the first drain 610 through the third via hole 530; the second flat layer 920 is formed with a fourth via hole 540 correspondingly above the ITO anode 1100 to expose a portion of the ITO anode 1100.
As manufacturing the dual gate oxide semiconductor TFT substrate, except the substrate 100, every other structure layer is implemented with the pattern process with one photo process. Thus, the number of the required photo processes is more. Obviously, the structure of the dual gate oxide semiconductor TFT substrate applicable for the OLED is more complicated. The procedure of the manufacture method is longer, and the production efficiency is lower, and the production cost is higher.